Spec Dinosauria: Therizinosauria
More like giant geese than non-avian maniraptorans, the strange, unwieldy therizinosaurs are decidedly odd members of the famously oddness-prone maniraptor clade. Like all maniraptors, therizinosaurs (or segnosaurs as they are synonymously called) are bipedal, covered in feathers, and have hands bearing three fingers each, but there the resemblance with the maniraptoran rootstock stops (if one doesn't plunge deep into the details of the skeleton). Segnosaurs are herbivores, and their bodies have radically changed to accommodate their vegetarian lifestyle. The hips of a segnosaur are much wider than is normal for a maniraptor, and the pubis is swept backward in the manner of a bird or ornithischian dinosaur, to make room the large belly needed to digest plant matter. Because of its tremendous gut, the centre of balance of a segnosaur is shifted backward along its spine, and these creatures squat like sumo wrestlers, with their torsos held further up than is normal for a dinosaur. (Like most dinosaurs, though, they cannot spread their legs.) To make matters even more confusing, the tiny, non-functional first toe possessed by most theropods has, in the segnosaurs, been greatly enlarged to make a decidedly un-theropodan four-toed foot. Misfits even in the varied and bizarre clade Maniraptora, and in the face of stiff competition from the hadrosaurs, ceratopsians, sauropods and other herbivores, the segnosaurs have nonetheless flourished in the past 130 million years, and have spread themselves across Eurasia and the Americas (with one species in the Sahara). The history of Therizinosaurria begins in the Early Cretaceous (but with a probably Jurassic record), when small browsers like †''Beipiaosaurus'' and †''Falcarius'' lived in the lush forests of Asia and western North America. By the end of the Mesozoic, the segnosaurs had expanded far into a herbivorous lifestyle, evolving into huge, lumbering forms like †''Segnosaurus'' and †''Therizinosaurus''. Fossil evidence is fairly poor for this time, with only a few decent partial skeletons and many puzzling fragments. Indeed, segnosaurs as a group were completely unknown until the 1970s, and early palaeontologists thought these long-necked plant eaters were late-surviving prosauropods (see cladogramme). In our own timeline, the segnosaurs' history ends at the end of the Cretaceous, but in Spec, the 'ground-sloth dinosaurs' continued through the end of Mesozoic and into the Cenozoic with little trouble. Eocene fossils from China hint at a truly huge therizinosaurid, †''Neonychus'', a close relative of the Cretaceous †''Therizinosaurus''. From the shoulder joint to the tip of the claw of the 2nd finger, its arms measured over 3 m in length. This giant, as well as all of the close relatives of †''Therizinosaurus'', went extinct at the end of the Eocene, but other segnosaur groups must have survived. Oligocene strata bear a large number of segnosaurs, including the newly-evolved arctotitanids (or robust segnosaurs), and the precursors of the ceratonychids (or hornclaws) were present as well. The Miocene was a time of great diversification for the therizinosaurs, with the fleet-footed ceratonychids roaming across the cold-temperate forests of the northern continents, and the arctotitanids expanding into a wide range of herbivore niches. As the globe cooled and then froze during the Pliocene and Pleistocene, the segnosaurs found themselves virtually alone in their ecosystems, being more cold-tolerant than the ceratopsians and hadrosaurs and better adapted for herbivory than the oviraptorosaurs. Almost immediately, these feathery plant-eaters took over the new taigas and tundras, evolving into the forms we know today: elk-like mooras, long-necked dorsas, and humongous arctotitans. Each retreat of the glaciers has seen a decrease in segnosaur range and sometimes diversity, especially amoung the specialized glaciotitanids. The partial thawing of Earth's polar reaches has each time allowed ornithischian herbivores, such as the formosicorns, the ceratopsians, the jackalopes and the viriosaurs to expand northward, chewing away at the therizinosaurs' strongholds, which in turn increased in every glacial period. The warm period of today is cooler than the last interglacial; there are none of these featherless herbivores left in Europe, which means that some segnosaur species extend all the way to the Mediterranean. In Asia and the Americas, however, these strange, lumbering maniraptors dominate the large herbivore guilds only in the frigid places, be they high in altitude or in latitude. But there they have evolved an impressive diversity. 'ARCTOTITANIDAE' (Robust segnosaurs) The clade which spawned the massive arctotitan, the arctotitanids are characterized by their robust body type, with short necks and tails. Quite successful during the ice ages, the arctotitanids seem to have declined somewhat since their heyday, with the ceratonychids (see below) far outnumbering them in population numbers and species count. These segnosaurs live in both Eurasia and the Americas, but their greatest diversity is to be found on the first of these two double continents. Yando (Ailurosaurus varius) The yando (Ailurosaurus varius) is the most southern of the modern arctotitanids, living in the Himalayan highlands. Yandos eat low-growing foliage, immature bamboo, fruits and nuts, but in times of famine (such as bamboo blooms), they don't refuse carrion. (fig. 1) Yando, Ailurosaurus varius (southwest China) Lammox (Tardox villosus) Lammoxes (Tardox villosus) are found across the harshest tundra of Eurasia and North America, moving in bands a few dozen individuals before the oncoming migration of the giant arctotians. These quarter-ton herbivores eat any plant material they can find, small trees, unappetizing ferns and mosses, and even lichens, which they scrape from rocks with their broad beaks. The ability to find food even on the bleak winter tundra makes lammoxes (and arctotitans, to a lesser extent) the nexus of a community of organisms that depend upon the therizinosaurs for survival, ranging from arctic plants to the bizarre caripoo, Spec's largest land mammal. Lammoxes protect themselves and each others from fendraks and polar draks with their long claws that are also used for digging for roots. (fig. 2) Lammox,'' Tardox villosus'' (circumpolar) The honas are the smallest of the therizinosaurs, usually weighing only about 50 kg. These miniature versions of the ice-age giants feed on seeds, berries, twigs and shoots, and occasionally small insects and reptiles. During the winter, they can sleep in small caves they dig in the snow, and even hibernate for several weeks if the weather becomes too harsh. Hona (Alpicosaura sp.) Alpicosaura nanus, the alpine hona, is the smallest therizinosaur in Spec, weighing only 20-30 kilograms. These small herbivores are adept climbers that eat a variety of foods ranging from moss to tree bark to insects. Male alpine honas are highly territorial, with adult cocks fiercely guarding their feeding grounds. These otherwise shy creatures will often kill each other over land disputes, but females and juveniles may travel with impunity. Another species of hona is the Snow hona (Alpicosaura similis) which can be found through out Northern Eurasia and North America. Arctotitan (Arctotitanus gigas) The arctotitan (Arctotitanus gigas) is the largest of the segnosaurs, a specialized relict left over from a chilly past. An arctotitan's claws are long and flattened side-to-side, forming tools the massive "woolly segnosaur" uses to dig for food under the snow. When feeding, the arctotitan lowers its head to the ground, its spine nearly horizontal, while its great claws plow through the snow. Its long, hollow, hair-like plumage covers almost all parts of its body, including the toes. The arctotitan is now in something of a decline, as the Ice Age's tundra have receded. Arctotitans now live only in the rather narrow arctotitan steppe belt around the Arctic Circle, and their extreme specialization to this habitat makes them very sensitive to environmental change. (fig. 4) Arctotitan,'' Arctotitanus gigas'' (Northern North America and Northern Eurasia) 'ALTOSECULINAE' (Upclaws and liandaolongs) The Americas, too, have segnosaurs clambering around in their mountains. First thought to be the honas' sistergroup, the upclaws have since turned out to be close relatives of the yando. Much like in the honas, their first toes have become long, mobile grasping devices that give a firm grip on rocky terrain, as well as (occasionally) on trees – upclaws are quite fond of conifer cones. Andean upclaw (Altoseculus andensis) Originally confined to the Rocky Mountains, the upclaws spread to the Andes soon after the Panama landbridge was established. (fig. 6) Bolívar's upclaw, Altoseculus andensis bolivari ''(Andes) The Andean upclaw (''Altoseculus andensis) exists in two distinct subspecies: A. a. peroni and A. a. bolivari. This species is spread across most of South America, from the Isthmus of Panama across the Andes to Tierra del Fuego. The subspecies A. a. bolivari inhabits the entire length of the Andes Mountains. These animals rarely reach lengths of over a meter. Individuals of A. a. bolivari have been seen sprawling some of the highest peaks in the world, and are known to be excellent climbers. Bolívar's upclaws are herbivores, which, although they prefer coniferous foliage, will ingest almost any vegetation. While A. a. bolivari ''is well adapted to its mountain habitat, ''A. a. peroni ''shows a slew of characters that enable it to survive in the high latitudes of Tierra del Fuego. Like ''A. a. bolivari, Perón's upclaws rarely reach more than a meter in length. This upclaw subspecies also favors coniferous foliage, but will eat berries and fruits if necessary. Populations of both subspecies are known to coexist in southern South America. Generally speaking, however, the two keep quite separate ranges. It is thought that the separation of a band of A. a. bolivari ''individuals 1.5 million years ago led to the evolution of ''A. a. peroni. This second subspecies came to occupy a small range of Tierra del Fuego, quite separate from that of its close relative. The exquisite timing of A. a. peroni's reproductive cycle made it further adapted to its environment, and has proven to be the key adaptation that separates the two subspecies. Northwestern Liandaolong'' (''Seculasaurus sylvis) Along the northwest coast of North America, between the Pacific Ocean and the Rocky Mountains, a narrow band of temperate rainforest extends north to south. This forest, cold in the winter, but with an annual rainfall equal to that of the Amazon, supports many animals and plants. One of the most common herbivores of this place is the northwestern (or blue-headed) liandaolong'' (''Seculasaurus sylvis). Although these two-meter herbivores are outwardly similar to the tirgs of the mountains, they are still liandaolong (sub-clade Liandaolongini): lowland creatures. Blue-head feathers are densely packed and oily, to shield the skin from the chilling damp, while the eyes and nostrils are placed high, to warn the herbivore of approaching predators. 'CERATONYCHIDAE' (Hornclaws) (fig. 7) The Three Eurasian lineages of Ceratonychidae to scale. (fig. 8) During the colder seasons horn claws, as in the case of this Siberian dorsa, (Ceratonyx major), ''can often be seen resting or sleeping with their necks tucked under the arm feathers to conserve heat. Since hornclaws are more or less social the whole of the year, there is usually at least one individual always keeping watch while the others sleep. As their common name implies, male hornclaws have very long manual talons that are mainly used for one purpose: showing off. The claws grow slowly during their adult life, and old hornclaws can have quite impressive weapons on their hands. Hornclaws very rarely engage in serious combat, though, but the claws can be lethal when used against predators like sabre-tyrants and veldraks. Having originated in North America, hornclaws soon reached Eurasia, where now most of their diversity can be found. One species specialised for life in deserts has even managed to dodge the competition from the jackalopes and lives in the Sahara. (fig. 9 and fig. 10) Head shapes of the moora (''Kentronyx robustus) and the European dorsa (Ceratonyx paluditus), two of the most common ceratonychid species. Dorsa and Moora (Ceratonyx ''sp.) Also called "sauropods-of-the-tundra" and "camel-geese", dorsas (''Ceratonyx) are slow-moving and placid creatures. These browsers usually stand still while eating, only moving their long neck to reach for the grass clumps or tender tree leaves. Dorsas inhabit the riverbanks and forest margins of northern and central Eurasia, where, during the summer migrations, they congregate around the many marshlands formed by the melting snow. Here the dorsas eat a variety of aquatic plants, grasses, and herbs, and storing much of what they eat in the form of a fatty hump over the hips. During the winter, dorsas move deeper into the forests, where they switch to high-browsing and pluck needles of the lower branches of the pine trees, supplementing this diet with the fat they stored during the summer. (fig. 11) A European dorsa, Ceratonyx paluditus, engaging in normal winter browsing behaviour, usually grazing in autumn to replenish its hump for the winter. . (eastern Eurasia) The Siberian dorsa, (Ceratonyx major) is the larger of the two dorsa species in Eurasia. During the summer these massive herbivores graze in swamps, plains and riversides, but during the winter they retreat to forests and switch to a diet consisting mainly of conifer needles. This change is also mirrored in the different types of stones they swallow during different parts of the year. Though similar to dorsas in size and convergently similar to the robust therizinosaurs, the moora (Kentronyx robustus) is probably more closely related to the panhas. Mooras live in the taiga of Eurasia, stripping the branches off trees and bushes. They can weigh up to half a ton, but still run surprisingly fast. Mooras, in fact, look a lot more robust than they really are because of their long hair-like plumage (especially during the winter). Like dorsas, mooras have humps on their backs for storing fat for the winter. (fig. 12) a female Moora, Kentronyx robustus ''(northern Eurasia) (fig. 13) A male moora in winter plumage Common Tirg (''Kentronyx americensis) (fig. 14) Common tirg, Kentronyx americensis, ''spotted jaub, ''Spadavis onca, and Baskerville, Metacanis phobos (northwestern North America) The common tirg (Kentronyx americensis) is one of the North American moora species. With its impressively long neck it can reach high leaves and needles. Its claws have shrunken; tirgs prefer to display the feather fan on the tip of their extra-long tails. Woolly Therizinosaur (Arctonyx americensis) At 10 meters in length, the woolly therizinosaur (Arctonyx americensis) is the largest of the herbivores of the North American tundra. This species eats grass and small plants, which it crops from the ground with a flattish-tiped beak. Its snout is elongated, and its eyes are set far up to give the best vision while grazing. In the winter, these dinosaurs grow shaggy coats of plumage, and the enlarged neural spines over their shoulders support fat stores for times of famine. Unlike the seculasaurids, which migrated to North America during the Miocene, the woolly therizinosaur is a ceronychid, closely related to the moora and panha that live just across the Bering Sea. 'CERATONYCHOIDINAE' (Panhas and lemeks) In the Miocene, a temperate steppe appeared in eastern Asia. No jackalopes or hadrosaurs lived there because it was too cold. A clade of hornclaws reacted, came out of the forests and evolved far-reaching adaptations for cursoriality (a few of which are already foreshadowed in the moora-tirg clade). For example, the back has again become horizontal, as usual among dinosaurs, and the tail vertebrae have lengthened to provide a means of balance. Though they have changed little since, the panhas are now the dominant plant-eaters of the polar and temperate open land of the northern continents. They also occur in the cold and temperate forests, where they eat mainly herbaceous vegetation in the clearings. Except in winter, they tend to leave most of the leaves and needles to the streks, which in turn are not good at eating grass. The lemeks have instead turned to even drier habitats. They live in the deserts of Asia as well as in the Sahara, thus representing the southernmost segnosaurs of the Old World. Tundra panhas are generalist/grazers, smaller and rather more common than the dorsas. These rather small herbivores live in great herds of 100 – 200 individuals that roam the tundra and taiga. In summer, these habitats supply the panhas with an abundance of grasses, herbs and shrubs, but during the autumn and winter, the great panha herds must break up into small family clusters that leave the plains to the lammoxes and migrate to the forests. There, the tundra panhas live through the harsh northern winter, subsisting upon fungi, lichens and moss dug from under the snow with their long, curved claws. In spring, the herds coalesce again, and the segnosaurs mate and lay their eggs. The fast-growing calves are usually ready to follow the herd as the first snow falls on the ground. Panha breeding grounds are often located on islands or river deltas where they are less accessible to predators. Shantak (Ceratonychoides ''sp.) The shantak (''Ceratonychoides gravis), which inhabits the Mongolian and Chinese steppes, is the largest panha species. Male shantaks have the proportionally longest arm claws of all extant hornclaws. (fig. 16) Shantak, Ceratonychoides gravis (eastern Asia) A new species of Shantak was found roaming in North America amongst a vast herd of migrating hmungos. The American Shantak (Ceratonychoides americanus) can be found through out most of North America, except on the eastern coast for reasons unknown. Growing up to lengths of 20 feet long, they are slightly larger than their Asia relatives and often lead a solitary life, for the most part. Lemek (Paraceratonyx ''sp.) The lemek (''Paraceratonyx mongoliensis) was at first commonly known as the desert dorsa, or camel dorsa, before it was shown that it did not belong to Ceratonyx after all. (The old common names are still often used, though neither was ever an official one.) Lemeks move around the central Asian steppes and semideserts in small herds, feeding on low-growing tough plants. The large hump on their back is partly supported by enlarged neural spines, and is used to store water and food in the form of fat. It seems that lemeks don't have to drink at all, but when water is available, they tend to take advantage of it. (fig. 17) Lemek, Paraceratonyx mongoliensis (central Asia) There is another Paraceratonyx species, the Arabian lemek (P. arabicus), which is smaller and has shorter and more downy feathers. The Arabian lemek is an unusual hornclaw for having chosen an extremely hot and arid environment instead of a chilly one. These inhabitants of the Arabian deserts and the Sahara can withstand long periods of drought without drinking, and often manage to get all the moisture they need from plants. MICROSEGNOSAURIDAE (Extinct) Microsegnosauridae, a group of small, insectivorous maniraptors was one of the stranger radiations of Therizinosauria. Evolving in the Oligocene, migrosegnosaurids became quite common during the Miocene and Pliocene, when they spread across Eurasia. Several well-preserved skeletons show small, lightly-built creatures with long, tubular snouts and powerful forelimbs. The retroverted pubis of the therizinosaurs was, with the microsegnosaurs, greatly reduced and pulled forward, like that of a basal coelurosaur, while the legs were reletively long and slender. The obvious explanation for these adapatations is that these dinosaurs were ant-eaters, although exactly why ants were so tempting as a food source that the therizinosaurs could completely abandon their former lifestyle and favor of their consumption is unknown. The early Oligocene microsegnosaurid Formicornithoides europeanus is the first known species of myrmicophagous therizinosaurs. When the fragmentary skull and limb material the species is known from was first discovered, it couldn't be indisputably identified as a therizinosaurid. It wasn't before the discovery of Microsegnosaurus myrmicophagus that the animal could be properly classified. 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